White light LED (light emitting diodes) have attracted an ever-widening attention due to advantages of high efficiency, long lifetime, small size, quick response, no pollution, and energy-saving. At present, one of the primary ways to achieve white light is to combine blue GaN chips with yellow YAG:Ce fluorescent powders. Such method has shortcoming of low color rendering index. However, the main trend and efforts have been directed toward combining near-ultraviolet LED chips and red, green, blue trichromatic powders to produce white light LED, which has high luminous efficiency, tunable color temperature, and high color rendering index. Consequently, LED trichromatic powders that can be efficiently excited by near-ultraviolet are currently studied widely. Therein, luminescent materials which take silicate systems as substrate have raised public concerns due to their features of wide source of raw materials, low-cost, good processing adaptability, moderate synthesis temperature and excellent stability.
Thomas synthesized alkaline-earth metals orthosilicate powders activated by bivalent europium ions. They are a kind of great green powders, compared to YAG fluorescent powders; they have broader excitation spectrum range, better color-purity. Nevertheless, such existing fluorescent powders have problems of low luminous efficiency, bad color rendering, etc.